Method of packaging a foodstuff



1952 R. L. DREYFUS ETAL 3,050,402

METHOD OF PACKAGING A FOODSTUFF Filed July 22, 1959 FIGZ.

FIG.4.

INVENTORS R ERT L. DREYF US J N W. HARRISON ATTORNEYS Stats 3,050,402LETHOD F PACKAGING A FOODSTUFF Robert L. Dreyfus and John W. Harrison,Arlington, Mass, assignors to W. R. Grace & Co., Cambridge, Mass acorporation of Connecticut Filed July 22, 1959, Ser. No. 828,770 1Claim. (Cl. 99171) This invention relates to open containers having atransparent protective film cover.

It has previously been proposed to use biaxially oriented, irradiatedpolyethylene film as a packaging material. Such irradiated polyethyleneperforms this function with eminent satisfaction. However, theirradiated polyethylene film is relatively expensive.

Accordingly, it is an object of the present invention to preparepackages utilizing the biaxially oriented, irradiated polyethylene inlesser amounts than has been utilized before.

An additional object is to form cardboard or other cellulosic containershaving a biaxially oriented, irradiated polyethylene film cover sealedthereto.

Still further objects and the entire scope of applicability of thepresent invention will become apparent from the detailed descriptiongiven hereinafter; it should be understood, however, that the detaileddescription and specific examples, while indicating preferredembodiments of the invention, are given by way of illustration only,since various changes and modifications within the spirit and scope ofthe invention will become apparent to those skilled in the art from thisdetailed description.

It has now been found that these objects can be obtained by coating acontainer of cardboard, paper or other cellulosic material with regularpolyethylene and then applying a cover of biaxially oriented, irradiatedpolyethylene and sealing the cover to the polyethylene coated surface ofthe cellulosic material.

In the illustrative examples, cardboard was coated with a conventionalpolyethylene, e.g. Alathon 16 which has a molecular weight of about20,000 and density of 0.923. The irradiated polyethylene was Alathonwhich had been irradiated to an extent of 12 megarad. and had then beenstretched 350% longitudinally and 350% laterally and had a shrink energyof 250 psi. at 96 C.

The invention will be best understood in connection with theaccompanying drawings wherein:

FIGURE 1 is an exploded perspective view of a backing board and coveraccording to the invention;

FIGURE 2 is a side view of the backing board and cover of FIGURE 1; V

:FIGURE 3 is a vertical section of the backing board of FIGURE 1;

FIGURE 4 is a vertical section showing frankfurters packaged in thecover and backing board of FIGURE 1;

FIGURE 5 is a top plan view partially broken away of another type ofcontainer and cover according to the invention.

Referring more specifically to the drawings, there is provided a backingboard 2. The backing board comprises a layer of cardboard 4 and an outerlayer of regular polyethylene 6.

Frankfurters 8 are positioned on the backing board 2 and then a cover ofthe biaxially oriented polyethylene film 10 is placed over thefrankfurters. The cover is bent around the backing board to provide anoverlapping film area 12. The overlapping film 12 is sealed to thepolyethylene 6 by the aid of a Teflon (polytetrafiuoroethylene) beltcovered hot plate (not shown). There was such a good bond between thebiaxially oriented, irradiated polyethylene cover and the regularpolyethylene that the paper board tore before it was possible to peelapart the seal. When the package was placed in water at 200 F. in orderto heat shrink the cover 10 tightly around the frankfurters 8, it wasobserved that the package stood up well under this treatment.

As shown in FIGURE 5, there is provided a rectangular container 14 inthe form of an inverted truncated pyramid. The container is made ofcardboard having an outer coating of regular polyethylene. A cover 16 ofbiaxially oriented, irradiated polyethylene of slightly greater areathan the top of the container is positioned over the container and isheat sealed to the regular polyethylene slightly below the top of thecontainer as indicated by the dotted lines 20. Hot air was utilized totake the Wrinkles out of the top surface of the cover film withoutdamage to the seal.

It will be evident that by use of the instant invention there is aconsiderable saving in the amount of biaxially oriented, irradiatedpolyethylene which is required since regular polyethylene is employed toserve a portion of its sealing function where the outstanding clarityand heat shrinking properties of the biaxially oriented, irradiatedpolyethylene is not required.

The biaxially oriented, irradiated polyethylene cover can be made withpleated or mitred corners. In one example, the cover film having mitredcorners was overlapped inch all around a backing board having theregular polyethylene as an outside coating. When sealed on the T efionbelt covered hot plate the irradiated polyethylene cover sealed to theregular polyethylene all around (and to itself at the pleated corners)with a considerable saving in cover film used over standard techniques,the plates made from the regular polyethylene coated cardboard not onlyare eminently waterproof and taste-free but by virtue of having theirradiated polyethylene fdrn covers sealed to their top edges can beused as individual butter plates, sandwich plates, pie plates, etc. Theseal can be made with a peelable bond if such is desired.

Bulky objects of irregular configuration, e.g. an egg beater, can befastened to a display card coated with regular polyethylene by using astrap'or band of the biaxially oriented, irradiated polyethylene andfastening it at the ends to the coated card. The strap or band can thenbe heat shrunk to tightly restrain the egg beater.

In general, as the irradiated polyethylene film, there can be employedpolyethylene which has been irradiated to an extent of 2 to megarad,preferably ,6 to 20 megarad. The irradiation can be accomplished inconventional fashion, eg by the use of a high voltage resonanttransformer, such as the 2,000,000 volt General Electric resonanttransformer, or high energy particle generators of 50,000 to 50,000,000volts or a Van de Graalf electron generator. In addition to the use ofelectrons, there can be employed any of the irradiation proceduresdisclosed in Baird application, Serial No. 713,848, filed February 7,1958, now Patent 3,022,543, issued February 27, 1962, or in RainerPatent 2,877,500.

The biaxial orientation is normally carried out to an extent of 100 to700% longitudinally and 100 to 900% laterally. The biaxial stretchingcan be carried out by blowing irradiated polyethylene tubing asdisclosed in the Baird application or can be accomplished as shown inthe Rainer patent. The irradiated, biaxially oriented polyethyleneprepared by such procedures has a high shrink energy, e.g.'100 to 1,000p.s.i. at 96 C.

There can be employed as the starting polyethylene for the irradiationprocedure high, low or medium density polyethylene prepared by low orhigh pressure technique. The starting polyethylene can have a molecularweight of 7,000 or 12,000 or 19,000 or 21,000 or 24,000 or 35,000 oreven higher.

The regular polyethylene utilized to coat the cardboard, paper or otherfibrous cellulosic material can be the same Patented Aug. 21, 1962 atedpolyethylene.

In addition'to frankfurters, other foodstufis can be packaged accordingto the invention, e.g. meats, such as hamburger, luncheon and slicedBologna, as Well as fruits, bern'es, e.g. strawberries, blackberries andblueberries, etc. The regular polyethylene can be utilized to coat oneor both surfaces of the cellulosic backing material. It is critical,however, that the irradiated, biaxially oriented polyethylene be adheredto the regular polyethylene to insure complete protection of thepackaged foodstuff.

What is claimed is:

A method of packaging a foodstufi comprising positioning the foodstuffon a fibrous cellulosic backing having an external coating of regularpolyethylene, placing a cover of irradiated, biaxially orientedpolyethylene, said irradiation being to an extent of 6 to 20 megarad,over said foodstufi and slightly overlapping said backing, heat sealingthe overlapped portion of said cover to the external coating ofpolyethylene on said ba cking' and-then heat shrinking said covertightly around. said foodstuff.

References (Zited in the file of this patent V UNITED STATES PATENTS IRamsbottom et al. Q Dec. 9, 1952 7 2,621,129 7 2,683,894 Kritchever uniJuly 20, 1954 1 2,715,075 Wolinski :Aug 9, 1955 2,808,192 Raisin Oct. 1,1957 2,844,517 Rainer et a1. ,Oct. 7, 1958 2,865,765 Allen Dec. 23, 19582,877,500 Rainer et al. Mar. 17, 1959 2,878,174 Rainer et al. Mar. 17,1959 OTHER REFERENCES Refrigerating Engineering, February 1954, pp.18-25. Nucleonics, vol. 12, No. 6, June 1954, pp. 18-25. l54lrradiatedPlastics.

